Jarad likes to eat big creatures. Check out Herd Gnarr. There's lots of ways of making big numbers of saprolings. Verdeloth the Ancient is a favorite. Verdeloth with a big kicker can make Herd Gnarr fairly huge. Ashnod's Altar can make big mana for the kicker cost, plus bonus damage if you've got Slimefoot out. Not a huge pricetag for any of them.
Well, I guess Ashnod's Altar's price has creeped up since I last checked.
Primalcrux can also get huge pretty quick. Especially with it's best friend Khalni Hydra.